1. Field
The inventive concept relates to an optical network system to which a network duplication way is applied.
2. Description of Related Art
In recent years, there have been popularized optical network systems, such as FTTH (Fiber to The Home), FTTB (Fiber to The Building), FTTC (Fiber to The Curb), etc., in which optical cables are installed to the subscriber's in-home network, in order to provide a high-speed and large capacity service to a subscriber as a high-speed internet service.
FIG. 1 illustrates a configuration of an active optical network system having a single optical link according to the prior art. Referring to FIG. 1, an upper network equipment 10 and a lower network equipment 30 are communicatively connected to each other through a transfer network equipment 20. For the above configuration, the network equipments 10, 20, and 30 are respectively provided with optical interface devices 11, 21, 22 and 31. However, in an optical network system having a single optical link as in FIG. 1, a transfer network cannot be duplicated. Therefore, when a failure occurs in the transfer network, there is a problem that a service is not sustainable until the failure is restored. The problem also exists in a network configuration of FIG. 6. Here, FIG. 6 illustrates an example in which the optical network configuration having a single link of FIG. 1 is applied to a base station transfer network.
In order to solve the aforementioned problem, as illustrated in FIG. 2, there has been proposed a method of using a network duplication-dedicated additional equipment in the prior art. FIG. 2 is a diagram for describing network duplication using the network duplication-dedicated additional equipment according to the prior art. Referring to FIG. 2, two transfer network equipments 20-1 and 20-2 are provided and a network duplication-dedicated additional equipment 40 for duplication connection with the lower network equipment 30 is further provided in order to duplicate the transfer network. In this case, the network equipments 10, 20-1, 20-2, 30 and 40 are respectively provided with optical interface devices 11-1, 11-2, 21-1, 21-2, 22-1, 22-2, 31, 41, 42-1, and 42-2 for communication connection as described above. According to the aforementioned network configuration, when a failure occurs in a working line (see reference symbols (a) and (c) in FIG. 2, for example), a service is continuously provided through a bypass path (see reference symbols (b) and (d) in FIG. 2).
However, the network configuration as in FIG. 2 necessarily requires an additional equipment for connection between the lower network equipment having a single link and the duplicated transfer network equipment (that is, the network duplication-dedicated additional equipment 40). Also, the network duplication-dedicated additional equipment 40 is capable of determining a failure occurring in an optical line (that is, reference symbols (c) and (d) in FIG. 2) between duplicated transfer networks, but occasionally does not detect a failure of an upper link (that is, reference symbols (a) and (b) in FIG. 2). Also, the network duplication-dedicated additional equipment 40 hardly detects a logical failure (for example, looping phenomenon) occurring in the transfer network equipments 20-1 and 20-2 themselves.